The following paragraphs are not an admission that anything discussed in them is prior art or part of the knowledge of persons skilled in the art.
Canadian Patent No. 2,139,560 describes a method of manufacturing a bulk bag comprising fabricating a fabric side wall structure and providing a plurality of lift loops each having a first and second leg portion. The legs of each lift loop are aligned at spaced locations around the top of the side wall structure, in positions for ready penetration by the tines of a forklift truck, with both leg portions of each lift loop extending a given distance downwardly from the top edge of the side wall structure. The leg portions of each of the lift loops are stitched to the top of the side wall structure by at least three parallel lines of high-strength thread, preferably by chain stitching or lock stitching. The stitching lines are all sewn in one or at most two passes; they extend horizontally across the lift loop legs to anchor the lift loops securely to the top of the side wall structure. There is no horizontal fold of the top of the side wall structure extending down to the anchor stitching.
U.S. Pat. No. 7,431,173 describes an intermediate bulk container comprising a storage container which is made from a suitable flexible material, a forklift pallet base including pole engaging formations on its upper surface which are arranged about its periphery, a plurality of poles the lower ends of which are releasably engageable with formations on the pallet base to provide a support cage for the storage container, a holed pole location member including pole engaging formations with which the upper ends of the poles are engageable to lock the poles together to inhibit transverse outward bulging of the storage container from between the poles and to preserve the container support cage against a load in the storage container with the underside of the pallet base and the upper surface of the pole locating member including formations, which are releasably engageable with compatible formations on containers below and above it in a stack.
U.S. patent application No. 20080137997 describes a stackable collapsible container for flowable materials. The container has a flexible outer skin and rigid support, having a top frame and bottom frame connected by poles. The top frame and bottom frame are designed for mating engagement when the containers are stacked, as well as for mating engagement when the containers are broken down for transport. The top frame and bottom frame are provided with similar perimeters to prevent undesired movement and contact between adjacent top frame when the containers are filled and transported.